It's as simple as this (excerpt from httpd.conf):

:

LoadModule dav_module /usr/lib/apache2/modules/mod_dav.so
LoadModule dav_fs_module /usr/lib/apache2/modules/mod_dav_fs.so

Alias /webdav /var/www/webdav

<Location /webdav>
DAV On
AuthType Basic
AuthName MyWebDAV
AuthUserFile /etc/apache/passwd.webdav
Require valid-user
</Location>

:

Create initial account:

htpasswd -c /etc/apache/passwd.webdav myuser

(You will be prompted for a password)
add accounts or change passwords:

htpasswd /etc/apache/passwd.webdav myuser2

(You will be prompted for a password)
Remove an account:

htpasswd -D /etc/apache/passwd.webdav olduser